This invention relates to apparatus for the assessment of a support surface such as a mattress, so as to determine objectively whether the support surface has worn out.
There are many instances where it is desirable to provide an objective test of the condition of a support surface such as a mattress. For example, it is known that mattresses have a finite life span and that after a period of use, they begin to lose their resilience and this leads to the phenomenon known as xe2x80x9cbottomingxe2x80x9d. This refers to the yielding of the mattress to such an extent that the occupant comes into contact with the hard base of the bed.
In hospitals, such a condition represents a serious hazard which greatly increases the risk of patients developing pressure sores. Since the treatment of pressure sores constitutes substantial expense to the hospital in terms of increased bed occupancy and nursing care, it is desirable to detect deterioration of mattresses at an early stage and dispose of them before the above hazardous condition is reached.
While fatigue of a mattress is related to its age, this is only one factor and masses and other support surfaces cannot be discarded simply on an age basis, since this would lead to disposal of many mattresses which are still in a serviceable condition.
The present established method of determining whether hospital mattresses are in a useable condition is the so-called xe2x80x9cnurse fist testxe2x80x9d. In this test, an experienced operative manually depresses the mattress at three defined points along it""s length and subjectively forms an opinion as to the condition of the mattress. However, this subjective test has been shown to suffer from poor repeatability and inter operator reliability.
The present invention, therefore, is directed to the provision of apparatus and method for objectively determining the condition of mattresses and other support surfaces, such as seats and wheelchair cushions.
U.S. Pat. No. 4,140,008 describes apparatus for measuring the firmness of a resilient object, such as a mattress. The apparatus described in this document comprises a platen, which is supported by a frame from a fixed base, and is drawn into the object by a motor.
According to one aspect of the present invention there is provided apparatus for assessing the condition of a person support surface which comprises a frame for extending over the support surface, an indenter mounted on said frame and a load sensor disposed between the indenter and the frame, means for pressing the indenter into the support surface, displacement measuring means for measuring the movement of the indenter into the support surface and data processing means for analysing the force applied to the indenter in relation to the displacement of the indenter into the support surface, characterised in that the apparatus is mobile and includes manually actuated means for pressing the indenter into the support surface.
In general, the apparatus according to the invention will be portable and has a frame which is supported either from the bed base below the mattress, or from a base member which is designed to extend beneath the bed base.
In a preferred form of the invention, the frame is supported in cantilever from one side of the support surface and the indenter is moved downwardly to depress the support surface by pressure applied to a handle by an operator. The frame may include guide means to guide movement of the indenter in an essentially vertical manner into contact with the support surface.
It has been found that a parallelogram frame is suitable to guide movement of the indenter along an essentially vertical path.
In the case of a hospital bed, the frame may be temporarily attached to the support frame of the bed, e.g. by a clamping device, and may be moved to different positions along the bed so as to test the mattress condition in the normal standard points along its length. These generally are one quarter, one half and three quarters of the distance from the head of the bed approximately along a centre line. In the case where the bed has no convenient frame for attachment of the testing apparatus, the frame may be in the form of a C-shaped structure having a base portion adapted to extend beneath the base of the bed, while the upper part of the frame extends over the mattress and enables the indenter to be brought into contact with the surface of the mattress.
The indenter preferably has a curved surface and may, for example, comprise a part of or a complete wheel or sphere.
In use, the indenter is depressed into the mattress until resistance is felt by the operator. A load cell mounted between the indenter and the frame measures the load applied, while displacement of the indenter into the bed is simultaneously measured by a suitable device. In the case where the whole or a part of the frame pivots in cantilever from a support, displacement is conveniently measured by means of a rotary potentiometer or equivalent rotation measurement device which measures pivoting movement of the frame and thus, indirectly, the displacement of the indenter.